This invention relates to a homogeneous analytical method for quantitative determination of substances contained in humors. More particularly the invention relates to an analytical method for the determination of antigens or antibodies in a homogeneous system which method comprises carrying out an antigen-antibody reaction using an enzyme-labeled antigen or antibody and measuring by a principally optical procedure changes in enzyme activity which takes place as a result of aggregation of the material.
The term "aggregation" used in this invention refers to association or amassing of a substance around an enzyme to such an extent as to exert a local change in enzyme activity and, for instance, it refers to immunological agglutination reactions involving biological factors such as agglutinin and other types of agglutination reactions such as those resulting from chemical crosslinking reactions.
Various methods have been proposed for immunologically determining substances contained in humors making use of an antigen-antibody reaction. For instance, methods based on the quantification of precipitate or agglutinate, such as capillary precipitation method, immunonephelometry, nephelometric immunoassay, latex agglutination method, single radial immunodiffusion, and the like are known as long-established techniques, and more recently there have been developed and widely used highly advanced methods, such as radio-immunoassay or enzyme immunoassay, which make accurate determination of even trace components possible by use of a labeled antigen or antibody. However, any of these methods has its own merits and demerits; some involve the problem in sensitivity and others are complicated in operation or have the problem in disposal of radioactive substances, and thus these known methods were unsuited or inconvenient for use in ordinary clinical tests.